Recently, environmental problems have become the foremost issue, and the use control to the surface treatments for automobile component parts, that is, to harmful substances, among them, to heavy metals (lead, cadmium, mercury and hexavalent chromium), has been strengthened, and their use has come to be restricted starting mainly in Europe.
Accordingly, rust-preventive coating films by means of Non-chromium Paint Processing System that does not include chromium have been developed (“On Non-chromium Paint Processing System” by FUKUSHIMA, pp. 18-22, March, 2004, RUST PREVENTION & CONTROL JAPAN, Japan Association of Corrosion Control). However, in these rust-preventive coating films that do not include chromium, the adhesiveness to substrate is low compared with that in conventional metallic powder-chromate chemical coating films that include chromium. In particular, in small-sized metallic component parts, such as wire springs in which steel wires, like piano wires and hard drawn steel wires being subjected to cold working, are adapted into the raw materials, the coated rust-preventive coating films cannot follow the elastic deformation of metallic component parts so that the micro-cracks or coming-off might occur. Moreover, such problems have arisen that, because of the vibrations when being transported or conveyed, component parts collide with each other and/or contact with each other slidingly and thereby the rust-preventive coating films come off partially to impair the appearance and additionally to degrade the corrosion resistance. Consequently, a rust-preventive metallic component part, which comprises a rust-preventive coating film whose adhesiveness to substrate is much stronger and firmer, and a manufacturing method for the same have been longed for.